Powder removal

ABSTRACT

A method includes issuing a state change fluid into an internal passage of an additively manufactured article and causing the state change fluid to change from a first state having a first viscosity to a second state that is either solid or has a second viscosity that is higher than the first viscosity within the internal passage. The method can also include causing the state change fluid to change back from the second state to the first state and flushing the state change fluid from the internal passage to remove residual powder from the additively manufactured article.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/924,046 filed Oct. 27, 2015, the entire contents of which areincorporated herein by reference.

BACKGROUND 1. Field

The present disclosure relates to additive manufacturing methods andsystems, more specifically to methods and systems for powder removal foradditively manufactured articles.

2. Description of Related Art

Certain methods for additive manufacturing using powder beds (e.g.,selective laser sintering) cause powder to be left within internalpassages of the additively manufactured article. Traditional methods forremoving of such remaining powder can damage internal passages, lead tomaterial weakness in the additively manufactured part, and/or leaveexcessive amounts of residual powder within the internal passages. Theability to effectively remove powder from certain types and/or sizes ofinternal features is a limiting design factor for AM articles.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for improved powder removal for additively manufacturedarticles. The present disclosure provides a solution for this need.

SUMMARY

A method includes issuing a state change fluid into an internal passageof an additively manufactured article and causing the state change fluidto change from a first state having a first viscosity to a second statethat is either solid or has a second viscosity that is higher than thefirst viscosity within the internal passage. The method can also includecausing the state change fluid to change back from the second state tothe first state and flushing the state change fluid from the internalpassage to remove residual powder from the additively manufacturedarticle.

The method can include applying vibration, such as ultrasonic vibration,to the additively manufactured article while the state change fluid isin the second state. Causing the state change fluid to change from thefirst state to the second state can include applying heat to the statechange fluid. For example, the state change fluid can includepoly(N-isopropylacrylamide) or any other suitable thermal-responsivepolymer that becomes more viscous or solidifies with added heat.

Causing the state change fluid to change from the first state to thesecond state can include cooling the state change fluid. For example,the state change fluid can include an ionic liquid that is crystallineat room temperature and melts to freely flow above room temperature. Incertain embodiments, the ionic liquid can include [bmim]NTf₂. In suchembodiments, the method can further include heating the ionic liquid tochange the ionic liquid from the second state to the first state beforeinputting the ionic liquid into the internal passage.

Causing the state change fluid to change from the first state to thesecond state can include applying a pressure or force to the statechange fluid. For example, the state change fluid can include anon-Newtonian fluid that becomes more viscous or rigid with appliedkinetic energy.

Inputting the state change fluid can include applying a pressure to thestate change fluid. Causing the state change fluid to change from thefirst state to the second state can include removing the appliedpressure or reducing pressure to the state change fluid. For example,the state change fluid can include a non-Newtonian fluid that flows morefreely with higher pressure (e.g., a clay suspension).

In accordance with at least one aspect of this disclosure, an additivelymanufactured article includes an internal passage, the internal passagesbeing cleared of residual powder by any suitable portion or combinationof portions of a method as described above.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,embodiments thereof will be described in detail herein below withreference to certain figures, wherein:

FIG. 1 is a flowchart of an embodiment of a method in accordance withthis disclosure;

FIG. 2 is a cross-sectional elevation view of an embodiment of anadditively manufactured article having an internal flow passage, showinga state change fluid flowing therethrough in a first state;

FIG. 3A is a cross-sectional elevation view of an the additivelymanufactured article of FIG. 2, showing the state change fluid convertedto a substantially solid form in an embodiment of a second state inaccordance with this disclosure; and

FIG. 3B is a cross-sectional elevation view of an the additivelymanufactured article of FIG. 2, showing the state change fluid convertedto a more viscous state in another embodiment of a second state inaccordance with this disclosure.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, an illustrative view of an embodiment of a method inaccordance with the disclosure is shown in FIG. 1 and is designatedgenerally by reference character 100. Other embodiments and/or aspectsof this disclosure are shown in FIGS. 2-3B. The systems and methodsdescribed herein can be used to remove residual powder from withininternal passages of additively manufactured articles, for example.

Referring to FIGS. 1 and 2-3B, a method 100 includes inputting (e.g., atblock 101) a state change fluid 205 into an internal passage 201 of anadditively manufactured article 200. The method 100 also includescausing (e.g., at block 103) the state change fluid 205 to change from afirst state having a first viscosity (e.g., as shown in FIG. 2) to asecond state that is either solid (e.g., as shown FIG. 3A) or has asecond viscosity that is higher than the first viscosity (e.g., as shownin FIG. 3B) while the state change fluid 205 is within the internalpassage 201.

The method 100 can also include causing (e.g., at block 105) the statechange fluid 205 to change back from the second state (e.g., FIG. 3Aand/or FIG. 3B) to the first state (e.g., FIG. 2). After converting backto the first state, the method 100 can include flushing (e.g., at block107) the state change 205 fluid from the internal passage 201 to removeresidual powder from the additively manufactured article 200.

Referring to FIGS. 3A and 3B, the method 100 can include applyingvibration 307 to the additively manufactured article 200 while the statechange fluid 205 is in the second state. In certain embodiments, thevibration can be ultrasonic vibration. Any other suitable mode ofvibration is contemplated herein and any type of transducer forvibration can be used to vibrate the additively manufactured article 200and/or the state change fluid 205 within the internal passage 201.

In certain embodiments, causing the state change fluid 205 to changefrom the first state to the second state can include applying heat tothe state change fluid 205. For example, the state change 205 fluid caninclude poly(N-isopropylacrylamide) or any other suitablethermal-responsive polymer that becomes more viscous and/or solidifieswith added heat.

Causing the state change fluid to change 205 from the first state to thesecond state can include cooling the state change fluid 205. Forexample, the state change fluid 205 can include an ionic liquid that iscrystalline at room temperature and melts to freely flow above roomtemperature. In certain embodiments, the ionic liquid can include[bmim]NTf₂. In such embodiments, the method 100 can further includeheating the ionic liquid to change the ionic liquid from the secondstate to the first state before inputting the ionic liquid into theinternal passage 201.

In certain embodiments, causing the state change fluid 205 to changefrom the first state to the second state includes applying a pressure orforce to the state change fluid 205. For example, the state change fluid205 can include a non-Newtonian fluid that becomes more viscous and/orrigid with applied kinetic energy (e.g., cornstarch in water).

In certain embodiments, inputting the state change fluid 205 includesapplying a pressure to the state change fluid 205. Causing the statechange fluid 205 to change from the first state to the second state caninclude removing the applied pressure or reducing pressure to the statechange fluid 205. For example, the state change fluid 205 can include anon-Newtonian fluid that flows more freely with higher pressure (e.g., aclay suspension).

In accordance with at least one aspect of this disclosure, an additivelymanufactured article 200 includes an internal passage 201, the internalpassage 201 being cleared of residual powder by any suitable portion orcombination of portions of a method 100 as described above.

Embodiments as described above allow for more effective powder removalthan traditional methods and systems. Increasing the viscosity of aflushing fluid (e.g., the state change fluid 205) can allow the flushingto be more effective. For example, vibrating the article 200 afterchanging to a more viscous or solid state translates the vibrationenergy to powder particles that are stuck inside the internal passage.This increase as energy translation improves particle separation fromthe internal passage, thereby cleaning out the internal passage betterwithout the need for corrosive or abrasive solutions which can comprisethe integrity of the article 200. This also allows for additivemanufacturing design freedom not previously attainable with traditionaltechniques.

The methods and of the present disclosure, as described above and shownin the drawings, provide for additively manufactured articles withsuperior properties including improved residual powder removal frominternal passages therein. While the apparatus and methods of thesubject disclosure have been shown and described with reference toembodiments, those skilled in the art will readily appreciate thatchanges and/or modifications may be made thereto without departing fromthe spirit and scope of the subject disclosure.

What is claimed is:
 1. An additively manufactured article having aninternal passage, wherein the internal passage is cleared of residualpowder by a method, the method comprising: issuing a state change fluidinto an internal passage of an additively manufactured article; causingthe state change fluid to change from a first state having a firstviscosity to a second state that is either solid or has a secondviscosity that is higher than the first viscosity within the internalpassage; causing the state change fluid to change back from the secondstate to the first state; and flushing the state change fluid from theinternal passage to remove residual powder from the additivelymanufactured article.